Structural evolution of a polynuclear hydroxyaluminum-montmorillonite complex with an 18.8 Å pillared structure on aging

A hydroxyl-Al-montmorillonite complex was prepared and then dried from suspensions under 0% RH. The complex was subsequently aged at room temperature under 0% RH or at ambient conditions («20% RH) for various lengths of time. Changes in the complex over 910 days were deduced by interpretation of X-ray diffraction and Fourier transform data. After 20 days, the initial 18.8-Â complex was transformed to a 28.4-Â complex which consists of 18.9-Â and 9.6-Â component layers. This complex gradually changed subsequently to a phase having a dominant 15.4-À peak with unclear peaks at 25 and 9.6-Â after 910 days. Fourier transform analysis indicated that the transformation of the 28.4-Â complex towards the final phase was characterized by the addition of a 14.3-Â component layer to the two component layers and the increasing abundance of the third component layer. As the abundance of the 14.3-Â component layer increased with a decrease in that of the 18.9-Â component layer, the former component layer appeared to increase at the expense of the latter. This suggests that the gibbsitic aluminum hydroxide sheets might be more favourable interlayer material than the blocky pillar molecules [Al₁₃O₁₀(OH)₂₄(H₂O₁₂)⁷⁺ in the 18.9-Â component layer. This structural evolution including the disintegration of the blocky pillar molecules to gibbsitic sheets gives a new insight into pedogenic chloritization of expandable layer silicates.Sing S. Shah, Kodama Hideomi. Structural evolution of a polynuclear hydroxyaluminum-montmorillonite complex with an 18.8 Å pillared structure on aging. In: Proceedings of the 9th international Clay Conference, Strasbourg, 1989. Vol II : Surface chemistry. Structure and mixed layering of clays. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1990. pp. 69-78. (Sciences Géologiques. Mémoire, 86